Plaster & render calculator

Gypsum plaster runs about 1 kg per m² per mm of thickness, cement render about 1.6–1.8 kg, and skim coat about 1–1.2 kg. At a typical 12 mm coat, that's roughly 12 kg/m² for gypsum and 20 kg/m² for cement render.

Undercoat plaster and render are usually 10–15 mm per coat; skim finishing is 2–3 mm. Very uneven masonry may need two undercoats — never try to pull 30 mm in one pass.

A 25 kg bag of gypsum plaster covers roughly 2 m² at 12 mm, or 9–12 m² as a 2–3 mm skim. Enter your own bag size in the calculator — coverage scales directly.

Gypsum plasters take roughly 0.5–0.7 L per kg, cement render about 0.2 L per kg of dry mix. Always follow the bag — too much water weakens any plaster.